Right. He hesitates, shifting his weight a bit. He's gotten lax here, let his guard down a little and has forgotten how to stay on his toes verbally with Tris. He hates sharing a room. He's always hated sharing a room. It makes him too exposed, too vulnerable. Tobias likes his privacy. He bites the tip of his tongue a second, debating on whether he should tell her or not.

"You don't have to. If you don't want to."

That's an opening to telling her, isn't it?